{"id":854509,"date":"2026-06-09T06:40:33","date_gmt":"2026-06-09T06:40:33","guid":{"rendered":"https:\/\/www.europesays.com\/us\/854509\/"},"modified":"2026-06-09T06:40:33","modified_gmt":"2026-06-09T06:40:33","slug":"top-comments-why-did-tyrannosaurus-rex-have-such-tiny-arms","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/854509\/","title":{"rendered":"Top Comments: Why Did Tyrannosaurus Rex Have Such Tiny Arms?"},"content":{"rendered":"
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Here at Top Comments we strive to nourish community by rounding up some of the site\u2019s best, funniest, most mojo\u2019d & most informative commentary, and we depend on your help!! Here\u2019s the new & improved DK6 version of how to submit nominations:<\/p>\n

If you see a comment by another Kossack that deserves wider recognition, please send it either to\u00a0topcomments at gmail dot com<\/strong>\u00a0or\u00a0send a kosmail to the username\u00a0topcomments<\/strong><\/a>\u00a0by 9:30pm Eastern. Please please include a few words about why you sent it in as well as your user name (even if you think we know it already :-)), so we can credit you with the find!<\/p>\n<\/blockquote>\n

When the first fossils of Tyrannosaurus rex were found, there was a great deal of doubt that the arms bones found with them, so much smaller in size than the rest of the animal, had anything to do with T. rex. A number of experts have taken to calling T. rex \u201ca mouth with legs,\u201d which is a pretty accurate description. When they finally accepted that these comparatively tiny arms did in fact belong to the carnivore, they have wrestled for more than a century about why they were so small, and what possible purpose they could have served for species. A new statistical study of comparative correlations among fossilized bones of 82 species of theropods<\/a> (two-legged carnivorous dinosaurs of which T. rex was the largest example) has suggested why their arms were so small.<\/p>\n

The shrinking of theropod forearms appears to correlate with the rise of giant sauropods (species like diplodocus and apatosaurus, herbivores that walked on 4 legs). When presented with the challenge of downing such large prey, claws were not nearly as effective as jaws. Evolutionary pressure favored such theropod species toward larger and stronger jaws while the arms became vestigial.<\/p>\n

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\u201cThe head took over from the arms as the method of attack. It\u2019s a case of \u2018use it or lose it\u2019 \u2013 the arms are no longer useful and reduce in size over time,\u201d said lead author Charlie Roger Scherer from UCL. \u201cThese adaptations often occurred in areas with gigantic prey. Trying to pull and grab at a 100ft-long sauropod with your claws is not ideal. Attacking and holding on with the jaws might have been more effective.<\/p>\n

\u201cWhile our study identifies correlations and so cannot establish cause and effect, it is highly likely that strongly built skulls came before shorter forelimbs. It would not make evolutionary sense for it to occur the other way round, and for these predators to give up their attack mechanism without having a backup.\u201d<\/p>\n<\/blockquote>\n

Small arm size correlated more strongly with skull robustness than skull size. However, the same correlation was observed regardless of the size of the theropod. Further, judging by the relative sizes of the hands to the arm bones of various species, it\u2019s clear that the evolutionary process of their shrinkage occurred by different processes. <\/p>\n

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The researchers noted that the forelimbs appeared to reduce in size in different ways, with hands and the lower part of the arm (past the elbow) shortening the most in abelisaurids (with late abelisaurids such as the Majungasaurus having exceptionally tiny hands). In tyrannosaurids, on the other hand, each element of the forelimb was reduced at a similar rate.<\/p>\n<\/blockquote>\n

I recall all manner of theories for how T. rex might have used its tiny arms, from performing some function during mating to using them as tooth picks, but accepting that they had become vestigial as they were no longer needed. After all, the same thing happened to the pelvis of the whale after its walking precursor had returned to the sea. As Stephen J. Gould often observed in his essays, once an anatomical feature of a species no longer serves a purpose, that species will eventually shed that feature through natural selection.<\/p>\n

On to the comments<\/strong><\/p>\n

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